The invention relates to industrial filter systems such as dust collectors of the type disclosed in U.S. Pat. No. 4,610,704. A conventional dust collector comprises a housing or hopper having a contaminated air inlet near its upper end, a dust discharge outlet at its lower end, and a clean air outlet intermediate the upper and lower ends. Supported within the housing are a number of generally cylindrical, hollow filter elements located between the contaminated air inlet and the clean air outlet such that contaminated air flows through the filter elements before leaving the housing through the clean air outlet. Each filter element has an open end communicating with a duct that in turn communicates with the clean air outlet. In order to remove contaminants accumulated on the filter elements, means are provided for directing a reverse flow of compressed air into the open end of each filter element. One such means is disclosed in Pat. No. 4,610,704. Other such means are disclosed in Pat. Nos. 4,666,472 and 4,789,387.